Laser irradiation method in which a distance between an irradiation object and an optical system is controlled by an autofocusing mechanism and method for manufacturing semiconductor device using the same

ABSTRACT

The present invention is to provide a laser irradiation method for performing homogeneous laser irradiation to the irradiation object even when the thickness of the irradiation object is not even. In the case of irradiating the irradiation object having uneven thickness, the laser irradiation is performed while keeping the distance between the irradiation object and the lens for condensing the laser beam on the surface of the irradiation object constant by using an autofocusing mechanism. In particular, when the irradiation object is irradiated with the laser beam by moving the irradiation object relative to the laser beam in the first direction and the second direction of the beam spot formed on the irradiation surface, the distance between the irradiation object and the lens is controlled by the autofocusing mechanism before the irradiation object is moved in the first and second directions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser irradiation method and moreparticularly to a laser irradiation method for controlling laserirradiation to an irradiation object by an autofocusing mechanism.Moreover, the present invention relates to a method for manufacturing asemiconductor device with the use of the laser irradiation method.

2. Related Art

In recent years, a technique to manufacture a thin film transistor (TFT)over a substrate has made a great progress, and application developmentto an active matrix display device has been advanced. In particular, aTFT formed using a poly-crystalline semiconductor film is superior infield-effect mobility to a TFT formed using a conventional amorphouscrystal semiconductor film, and therefore high-speed operation ispossible when the TFT is formed using the poly-crystalline semiconductorfilm. For this reason, it has been tried to control a pixel by a drivercircuit formed over the same substrate as the pixel, which has beenconventionally controlled by a driver circuit provided outside thesubstrate.

A substrate used in a semiconductor device is expected to be a glasssubstrate in terms of cost. However, the glass substrate is inferior inheat resistance and easy to change in shape due to the heat. Therefore,when the TFT using the poly-crystalline semiconductor film is formedover the glass substrate, laser annealing is employed to crystallize asemiconductor film formed over the glass substrate in order to preventthe glass substrate from changing in shape due to the heat.

Compared with another annealing method which uses radiant heat orconductive heat, the laser annealing has advantages that the processingtime can be shortened drastically and that a semiconductor substrate ora semiconductor film over a substrate can be heated selectively andlocally so that the substrate is hardly damaged thermally.

In general terms, the laser annealing to the semiconductor film is oftenperformed by using an excimer laser. The excimer laser has advantages ofits high output power and high repetition rate. Moreover, the laser beamemitted from the excimer laser has an advantage that it is sufficientlyabsorbed in a silicon film, which is often employed as the semiconductorfilm. In the laser irradiating step, a beam spot of the laser beam onthe irradiation object is shaped into a linear spot (includingrectangular and elliptical spots) by an optical system, and the beamspot is moved relative to the irradiation object in a short-sidedirection of the linear beam spot. By such laser irradiation, the laserannealing can be performed to the irradiation object effectively.

Moreover, a continuous wave laser (also referred to as a CW laser) canbe used in the laser annealing step. When a laser beam emitted from theCW laser is shaped into a linear spot and the semiconductor film, whichis the irradiation object, is moved relatively in the short-sidedirection of the beam spot on the irradiation object, a large crystalgrain extending long in the moving direction can be formed in thesemiconductor film. A TFT manufactured in accordance with the extendingdirection of the large crystal grain can have higher carrier-mobilitythan a TFT manufactured using the excimer laser. With the TFT havinghigh carrier-mobility, the circuit can be driven at higher speed, andtherefore a driver, a CPU, and the like can be manufactured.

The laser beam emitted from the CW laser to be generally used in thelaser annealing has a wavelength of 532 nm because this wavelength issufficiently absorbed in amorphous silicon (a-Si) and the conversionefficiency from the fundamental wave by the non-linear optical elementis high. Usually, the shorter the wavelength of the laser beam is, themore a-Si absorbs the laser beam. Meanwhile, the shorter the wavelengthis, the lower the power of the laser beam is.

A technique for forming the TFT with the use of the semiconductor filmcrystallized by the above method has been carried out in many fields.

When the power of the laser beam is low, the laser beam is condensed onone point in the irradiation object by a lens in order to increase theenergy density or the power density of the laser beam. Moreover, even inthe case of forming a pattern on the irradiation object directly byirradiating the irradiation object with the laser beam, the beam spot iscondensed on the irradiation object by the lens. For example, when thesemiconductor film is crystallized using the CW laser, the beam spot isshaped into an elongate spot such as a rectangular, elliptical, orlinear spot on the irradiation object and condensed to have a length ofseveral μm in the short-side direction by the lens in order to increasethe throughput as much as possible. Furthermore, when a fine pattern isimaged directly to the irradiation object by the laser irradiation, thebeam spot is narrowed further.

To narrow the diameter of the beam spot formed over the irradiationobject by condensing the laser beam, it is necessary to use a lenshaving large numeral aperture (NA). Generally, NA and a focal depth Zsatisfy the equation Z=±λ/2NA² where λ is the wavelength of the laserbeam. Therefore, when the lens has larger NA, the focal depth of thelens becomes shorter accordingly. For example, when using the CW laser,the focal depth needs to be adjusted to be approximately several μm.

However, when a substrate typified by a glass substrate becomes larger,the variation of the thickness of the substrate becomes more remarkable.The thickness may vary within the substrate by several tens μm. Forexample, when the semiconductor film formed over the glass substrate orthe like whose thickness is not even is annealed by the laserirradiation, the distance between the lens and the irradiation objectdepends on the location in the substrate, and the beam spot shapechanges depending on the location accordingly. For this reason, thecrystallinity differs depending on the location even in thesemiconductor film formed over the same substrate.

SUMMARY OF THE INVENTION

In view of the above problem, it is an object of the present inventionto provide a laser irradiation method for irradiating an irradiationobject with the laser beam homogeneously even when the thickness of theirradiation object is not even. It is another object of the presentinvention to provide a method for manufacturing a semiconductor devicewith the use of the laser irradiation method.

The present invention discloses a laser irradiation method in which thelaser irradiation is performed while keeping the distance between theirradiation object and the lens for focusing the laser beam on theirradiation object constant by using the autofocusing mechanism.Particularly, in the case of performing the laser irradiation by movingthe irradiation object relative to the laser beam incident thereinto ina first direction and a second direction of the beam spot formed overthe irradiation object, the distance between the lens and theirradiation object is controlled by the autofocusing mechanism beforethe irradiation object moves in the first and second directions. It isto be noted that the autofocusing mechanism is for adjusting the focalpoint of the laser beam delivered to the irradiation object through thelens on the irradiation object.

In the case of performing the laser irradiation to the irradiationobject including a swell, the autofocusing is conducted in advance inconsideration of the swell. For example, when the swell exists along thefirst direction of the irradiation object and the laser irradiation isperformed in the first direction and the second direction perpendicularto the first direction, the autofocusing may be conducted before movingthe irradiation object in the second direction where the swell does notexist.

Specifically, the autofocusing mechanism corrects the change of thedistance between the lens and the irradiation object due to the swell ofthe substrate after moving the irradiation object relative to the laserbeam incident into the irradiation object in the first direction wherethe swell exists. The autofocusing mechanism may control the distancebetween the lens and the irradiation object while moving the irradiationobject in the first direction where the swell exists.

The beam spot formed on the irradiation object can be shaped into arectangular spot or an elongate spot such as an elliptical or linearspot having a short side and a long side by the optical system. Thelaser irradiation can be performed effectively when the elongate beamspot is formed so that the long side of the beam spot is parallel to thefirst direction where the swell exists. The optical system hereindescribed is a combination of one or a plurality of lenses and mirrorsfor condensing the laser beam on any portion.

The laser irradiation may be performed to the irradiation object bymoving one or both of the irradiation object and the laser beam. It ispreferable to move one or both of the irradiation object and the laserbeam more slowly in the first direction where the swell exists than inthe second direction because the irradiation position can be controlledwith high accuracy and the homogeneous irradiation becomes possible.

To conduct autofocusing, any method may be employed when the laser beamcan be focused on the surface of the irradiation object. For example, alaser beam and a detector for detecting the laser beam (four-arrayphotodetectors, a CCD (Charge Coupled Device), a PSD (Position SensitiveDetector), or the like) may be used. The laser beam can be constantlyfocused on the irradiation object by measuring the distance between thelens and the irradiation object with these laser beam and detector andkeeping the distance therebetween constant. The distance between thelens and the irradiation object can be controlled by providing amicro-motion device to the lens or the stage. Moreover, the laser beamfor measuring the distance between the lens and the irradiation objectmay be provided separately from the laser beam for annealing theirradiation object, or may be also used as the laser beam for annealingthe irradiation object. As another autofocusing method, a method usedfor playing a CD, a DVD, or the like (for example, an astigmatic method,a knife edge method, a Foucault method, or a critical angle method) canbe used. Moreover, it is possible to control the distance between thelens and the irradiation object by directly contacting a contactdisplacement sensor to the irradiation object. The distance between thelens and the irradiation object may be controlled by the autofocusingmechanism while moving the optical system including the lens or movingthe irradiation object.

When the annealing is performed by irradiating the semiconductor filmwith the laser beam according to the above-mentioned laser irradiationmethod, the semiconductor film can be crystallized or activated, forexample. Moreover, the annealed semiconductor film can be used tomanufacture a semiconductor device.

The laser oscillator used in the present invention is not limited inparticular, and the pulsed laser oscillator or the continuous wave (CW)laser oscillator may be used. The pulsed laser is, for example, anexcimer laser, a YAG laser, or a YVO₄ laser. The CW laser is, forexample, a YAG laser, a YVO₄ laser, a GdVO₄ laser, a YLF laser, or an Arlaser. By using the CW laser beam, it is possible to form a largecrystal grain extending long in the scanning direction of the laserbeam. Furthermore, a pulsed laser oscillator with a repetition rate of10 MHz can be used. The large crystal grain extending long in thescanning direction can be obtained even by using a laser beam emittedfrom a pulsed laser oscillator with the repetition rate of 10 MHz ormore (this laser beam is also referred to as a quasi-CW laser beam).

According to the present invention, the laser irradiation can beperformed homogeneously even when the thickness in the irradiationobject is not even. Moreover, the laser irradiation can be performedeffectively by performing the laser irradiation in consideration of theswell of the irradiation object.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a drawing showing a laser irradiation method of the presentinvention;

FIG. 2 is a drawing showing the relation between an optical path lengthand the shape of a beam spot in an optical system;

FIGS. 3A to 3E are drawings showing the relation between four-arrayphotodetectors and a beam spot;

FIG. 4 is a drawing showing a laser irradiation method of the presentinvention;

FIG. 5 is a drawing showing an optical system;

FIG. 6 is a drawing showing an autofocusing mechanism;

FIGS. 7A to 7C are a drawing showing an autofocusing mechanism;

FIG. 8 is a drawing showing a laser irradiation method of the presentinvention;

FIG. 9 is a drawing showing a laser irradiation method of the presentinvention;

FIG. 10 is a drawing showing a laser irradiation method of the presentinvention;

FIGS. 11A to 11E are drawings showing steps for manufacturing asemiconductor device using a laser irradiation method of the presentinvention;

FIGS. 12A to 12E are drawings showing steps for manufacturing asemiconductor device using a laser irradiation method of the presentinvention;

FIGS. 13A and 13B are drawings showing steps for manufacturing asemiconductor device using a laser irradiation method of the presentinvention;

FIG. 14 is a drawing showing a laser irradiation method of the presentinvention;

FIG. 15 is a drawing showing a laser irradiation method of the presentinvention;

FIGS. 16A to 16H are drawings showing electronic instrumentsmanufactured by applying a laser irradiation method of the presentinvention; and

FIGS. 17A and 17B are drawings showing a laser irradiation method of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION Embodiment Mode

Embodiment modes of the present invention are hereinafter described withreference to the drawings. However, since the present invention can beembodied in many different modes, it is easily understood by those whoare skilled in the art that the mode and the detail of the presentinvention can be changed and modified within the content and the scopeof the present invention. Therefore, the present invention is notlimited to the description of the embodiment modes. Moreover, the samereference numeral is given to the same part through the drawings.

In the present invention, the laser irradiation is performed to theirradiation object while keeping the distance between the lens and theirradiation object constant by the autofocusing mechanism. Theautofocusing mechanism comprises a detector for detecting whether thefocal point of the laser beam that is irradiated to the irradiationobject through the lens is on the surface of the irradiation object, anda controller for controlling the distance between the lens and theirradiation object. To control the distance between the lens and theirradiation object, two methods are given, in one of which theirradiation object is moved and in the other of which the optical systemincluding the lens is moved.

Moreover, when the irradiation object has regular swell, the laserirradiation is performed in consideration of the swell. For example, aglass substrate usually has a swell in a certain direction due to itsmanufacturing process. Therefore, in the case of using a glasssubstrate, the autofocusing mechanism is used to adjust the focal pointon the irradiation object only when the substrate is moved in thedirection where the swell exists, while the autofocusing mechanism maynot be used when the substrate is moved in the direction where the swelldoes not exist.

For example, the irradiation object can be irradiated with the laserbeam in the present invention as follows: the semiconductor film isannealed with the laser beam; a semiconductor film is activated byirradiating the semiconductor film with the laser beam; the irradiationobject is microprocessed by the photolithography technique; or a patternis formed by direct laser irradiation. Moreover, the present inventionis not limited to these examples, and includes any kinds of steps inwhich the irradiation object is processed by laser irradiation.

The laser oscillator used in the laser irradiation is not limited inparticular, and the pulsed laser oscillator or the CW laser oscillatormay be used. Moreover, the pulsed laser oscillator with a repetitionrate of 10 MHz or more can be used.

Embodiment Mode 1

With reference to FIG. 1, this embodiment mode 1 describes aconfiguration for controlling the distance between a lens and anirradiation object by moving the irradiation object according to thelaser irradiation method using an autofocusing mechanism.

In FIG. 1, a first laser beam is emitted from a laser oscillator 101having a repetition rate of 10 MHz or more, and is reflected on a mirror102 so as to be incident vertically into an irradiation object 106.After that, the first laser beam is incident into cylindrical lenses 103and 104 which respectively act on different directions, and thencondensed on the irradiation object 106. Thus, a linear beam spot 105 isformed on the irradiation object 106.

Although the laser oscillator 101 is a laser oscillator with arepetition rate of 10 MHz or more, the present invention is not limitedto this, and a CW laser oscillator may be used. In the case of using theCW laser oscillator, the first laser beam is made incident obliquely ata certain angle or more, not vertically, into the irradiation object toavoid the interference between the reflected beam and the incident beamon the irradiation object. In this case, the incidence angle Θ of thelaser beam may satisfy the inequality of Θ=tan⁻¹ (l/2d) where I is thelength of the beam spot in the incident direction of the laser beam andd is the thickness of the irradiation object.

The irradiation object 106 can be moved by a Z-axis stage 116, an X-axisstage 117, and a Y-axis stage 118. The Z-axis stage 116 can adjust thetilt of the irradiation object 106 and move the irradiation object 106upward or downward. In this embodiment mode, the first laser beam isdelivered to the irradiation object 106 by moving the X-axis stage 117and the Y-axis stage 118.

To keep the distance between the irradiation object 106 and each of thecylindrical lenses 103 and 104 constant, an autofocusing mechanismincluding a laser oscillator 109, cylindrical lenses 110 and 111,four-array photodetectors 112, and the Z-axis stage 116 is used. To keepthe distance between the irradiation object 106 and each of thecylindrical lenses 103 and 104 constant means to keep the focal point ofthe cylindrical lenses 103 and 104 on the irradiation object 106. It isto be noted that the distance between the cylindrical lenses 103 and 104is fixed. When the focal point of the cylindrical lens 104 is on thesurface of the irradiation object 106, the focal point of thecylindrical lens 103 is also on the surface of the irradiation object106.

A second laser beam emitted from the laser oscillator 109 is incidentinto the irradiation object 106 through the two cylindrical lenses 110and 111, and the laser beam reflected on the irradiation object 106 isdetected with the four-array photodetectors 112. Here, the optical pathlength of the second laser beam changes when the surface of theirradiation object 106 gets higher or lower. The four-arrayphotodetectors 112 convert the detected beam into an electric signal inproportion to the intensity of the beam. Based on this electric signal,the Z-axis stage 116 working with the four-array photodetectors 112 ismoved so as to keep the distance between the cylindrical lens 104 andthe irradiation object 106 constant. It is preferable to make the secondlaser beam incident obliquely into the surface of the irradiation object106 as shown in FIG. 1. In this case, since the first laser beam is madeincident vertically into the irradiation object 106 and the second laserbeam is made incident obliquely into the irradiation object 106, it ispossible to provide the optical systems for emitting the first laserbeam and the second laser beam in different positions, and thisconfiguration facilitates the construction of the optical system.

With reference to FIG. 2, a relation between the beam shape and theoptical path length in the optical system including two cylindricallenses is described.

At the position of a plane 112 b in FIG. 2, the first laser beam shownin FIG. 1 is focused on the irradiation object 106. Here, the focalpoints of the two cylindrical lenses 110 and 111 are adjusted so thatthe beam spot becomes circular on the irradiation object 106.

When the irradiation object 106 comes closer to the cylindrical lens104, the beam spot becomes elliptical, as shown at the plane 112 a,because the optical path length becomes shorter. On the other hand, whenthe irradiation object 106 goes farther from the cylindrical lens 104,as shown at the plane 112 c, the beam spot becomes elliptical in adirection perpendicular to the ellipse formed at the plane 112 a becausethe optical path length becomes longer. Moreover, when the irradiationobject 106 goes much farther, as shown at the plane 112 d, the intensityof the laser beam becomes lower, and the value detected by thefour-array photodetectors becomes lower.

In the case of providing the irradiation object 106 in a tilted state,the reflected laser beam does not reach the four-array photodetectors112, and therefore the current value is not detected. Even if thereflected beam reaches the four-array photodetector 112, the differentcurrent values are detected by the respective four photodetectors.

Next, the relation between the four-array photodetectors and the beamspot is described with reference to FIGS. 3A to 3E.

In FIGS. 3A to 3E, each of the four-array photodetectors is denoted withreference characters (a) to (d). When the beam is delivered to eachphotodetector, the beam is converted into electricity in proportion tothe intensity of the beam.

When the optical path length is short as shown in FIG. 3A, which meanswhen the distance between the cylindrical lens 104 and the irradiationobject 106 is shorter than the focal length of the cylindrical lens 104,the beam spot formed at the four-array photodetectors is elliptical. Thecurrent value detected thereby is (a)=(c)<(b)=(d). To provide theirradiation object 106 at the focal point of the cylindrical lens 104,the Z-axis stage 116 may be moved in a direction apart from thecylindrical lens 104.

When the optical path length is appropriate as shown in FIG. 3B, whichmeans when the distance between the cylindrical lens 104 and theirradiation object 106 is the same as the focal length of thecylindrical lens 104, the beam spot at the four-array photodetectors iscircular. The current value detected thereby is (a)=(b)=(c)=(d).

When the optical path length is long as shown in FIG. 3C, which meanswhen the distance between the cylindrical lens 104 and the irradiationobject 106 is longer than the focal length of the cylindrical lens 104,the beam spot at the four-array photodetectors is elliptical. Thecurrent value detected thereby is (a)=(c)>(b)=(d). To provide theirradiation object 106 at the focal point of the cylindrical lens 104,the Z-axis stage 116 may be moved in a direction toward the cylindricallens 104.

When the optical path length is extremely long as shown in FIG. 3D,which means when the distance between the cylindrical lens 104 and theirradiation object 106 is much longer than the focal length of thecylindrical lens 104, the beam spot at the four-array photodetectors iselliptical, and a part of the beam spot is not incident into thefour-array photodetectors. Here, the total current value metered by therespective photodetectors is low because of the part of the beam spotnot incident into the photodetectors. In this case, as is in FIG. 3C,the Z-axis stage 116 may be moved in a direction toward the cylindricallens 104.

When the optical path length is appropriate and the irradiation object106 is tilted as shown in FIG. 3E, which means when the plane portion ofthe cylindrical lens 104 is not parallel to the surface of theirradiation object 106, the beam spot at the four-array photodetectorsis circular. In this case, the current value metered by the four-arrayphotodetectors is (a)>(b)=(d)>(c). In the photodetectors, only (b) and(d) have the same current value, while (a) and (c) do not. In this case,the Z-axis stage 116 may be adjusted so as to tilt toward the four-arrayphotodetectors.

As thus described, the Z-axis stage 116 may be controlled so that theintensity of the laser beam delivered to the four-array photodetectorsis constant at all of the four photodetectors.

The irradiation object 106 may be formed of any kind of materials whichcan be processed by the laser irradiation. Specifically, the irradiationobject 106 may be, for example, a semiconductor; a semiconductor filmformed over a substrate of glass, plastic, or the like; metal; anorganic resin film; or the like. When the irradiation object 106 is thesemiconductor film formed over the glass substrate, the semiconductorfilm can be annealed by irradiating the semiconductor film with thelaser beam. Even when the thickness of the semiconductor film is noteven due to the unevenness of the glass substrate, the semiconductorfilm can be annealed homogeneously because the laser irradiation can beperformed with the autofocusing mechanism. Moreover, when theirradiation object 106 is the organic resin film, the organic resin filmcan be patterned or have an opening therein by the laser irradiation. Byperforming the laser irradiation with the autofocusing mechanism in sucha way that the laser beam is focused correctly on the surface of theorganic resin film, a pattern and an opening can be formed correctly.

Although the present embodiment mode has described the example of usingthe four-array photodetectors to detect the second laser beam, thepresent invention is not limited to this, and a CCD, a PSD, or the likecan be used to detect the second laser beam. Furthermore, instead of thesecond laser beam, it is possible to use a contact displacement sensorwhich directly contacts the irradiation object 106, an electrostaticcapacity displacement sensor which uses the change of the electrostaticcapacity, an eddy current displacement sensor which uses high-frequencymagnetic field as the autofocusing mechanism.

Although the first laser beam emitted from the laser oscillator 101 withthe repetition rate of 10 MHz or more is incident vertically into theirradiation object 106 in this embodiment mode, the laser beam may bemade incident obliquely in the same manner as when using the CW laser.In this case, it is preferable to make the second laser beam emittedfrom the laser oscillator 109 incident vertically. By making the secondlaser beam incident vertically when the first laser beam is madeincident obliquely, the optical systems for shaping the first and secondlaser beams do not overlap each other; therefore, the optical systemscan be easily assembled. Moreover, when the second laser beam is madeincident vertically, the second laser beam can be easily delivered tothe vicinity of the beam spot of the first laser beam formed on theirradiation object 106, and accordingly, the accuracy of autofocusingcan be improved.

By providing the autofocusing mechanism in the above laser irradiation,it is possible to perform laser irradiation while controlling thedistance between the lens and the irradiation object.

Embodiment Mode 2

It is preferable to perform autofocusing all the time in order to havethe focal point of the laser beam condensed by the lens on theirradiation object. However, when the swell or the like on theirradiation object is known in advance, the autofocusing may beperformed only as necessary to increase the processing efficiency. Thisembodiment mode describes a laser irradiation method when the glasssubstrate has the swell along a certain direction with reference to FIG.8.

Generally, a larger glass substrate has a swell more easily, which areunique to the manufacturing process of the glass substrate. The swellchanges based on the function having one or less inflection points inthe glass substrate and exists along a certain direction. Meanwhile, theswell does not exist in the direction perpendicular to the directionwhere the swell exists. For this reason, the laser irradiation ispreferably performed in consideration of the unique characteristic of aglass substrate.

In FIG. 8, since a semiconductor film 206 is formed over a glasssubstrate having a swell in one direction, the surface of thesemiconductor film 206 swells in reflection of the swell of the glasssubstrate. In the same manner as FIG. 1, the first laser beam is emittedfrom the laser oscillator 101 (a CW laser or a pulsed laser with therepetition rate of 10 MHz or more) and reflected on a mirror 102. Then,the laser beam is incident vertically into the semiconductor film 206.After that, the first laser beam is incident into cylindrical lenses 103and 104, and focused on the semiconductor film 206 formed over the glasssubstrate. Thus, the first laser beam is shaped into a linear beam spot105 on the semiconductor film 206. When a CW laser oscillator is used asdescribed above, the first laser beam may be made incident into thesemiconductor film 206 at a certain angle, but not vertically.

In a three-dimensional configuration including an X-axis, a Y-axis, anda Z-axis, the glass substrate is provided in an X-Y axes plane. TheX-axis direction is a direction where the glass substrate does not havethe swell, the Y-axis direction is a direction perpendicular to theX-axis direction, and the Z-axis direction is a direction perpendicularto the X-axis and Y-axis directions. In this case, the glass substratehas the change to the Z-axis direction only in the Y-axis direction, butnot in the X-axis direction. In other words, the glass substrate has theswell only in the Y-axis direction. Here, the linear beam is formed sothat its short-side direction is parallel to the direction where theglass substrate does not have the swell (X-axis direction). The movementof the glass substrate is controlled by an X-axis stage 117, a Y-axisstage 118, and a Z-axis stage 116. The X-axis stage 117 moves the glasssubstrate in the X-axis direction, and the Y-axis stage 118 moves it inthe Y-axis direction. The Z-axis stage 116 adjusts the tilt of the glasssubstrate and moves it in the Z-axis direction.

In the embodiment mode 2, the laser irradiation is performed whilemoving the semiconductor film 206, which is the irradiation object, inthe X-axis and Y-axis directions. The annealing is performed in such away that the semiconductor film 206 is irradiated with the first laserbeam when the semiconductor film 206 moves in the short-side direction(X-axis direction) of the linear beam spot.

After moving the semiconductor film 206 in the X-axis direction todeliver the first laser beam from one end to the other end of thesubstrate, the semiconductor film 206 is moved in the Y-axis direction.The semiconductor film 206 is moved in the Y-axis direction to determinewhere to anneal in the X-axis direction next. For example, when thewhole surface of the substrate is annealed, the semiconductor film 206is moved in the Y-axis direction by the length of the linear beam spotin the long-side direction, and then the laser irradiation is performed.

Although the laser irradiation is performed by moving the semiconductorfilm 206 by the X-axis stage 117 and the Y-axis stage 118 while fixingthe first laser beam in this embodiment mode, the laser irradiation maybe performed by moving the laser beam while fixing the semiconductorfilm 206. Alternatively, both of the semiconductor film 206 and thelaser beam may be moved to perform the laser irradiation.

Since the variation of thickness of the substrate in the X-axisdirection is small, the distance between the cylindrical lens 104 andthe semiconductor film 206 hardly changes even when the laserirradiation is performed by moving the semiconductor film 206 in theX-axis direction. On the other hand, since the glass substrate has theswell unique to the glass substrate in the Y-axis direction, thedistance between the cylindrical lens 104 and the semiconductor film 206changes with the movement of the semiconductor film 206 in the Y-axisdirection.

When the swell exists in a certain direction, the autofocusing does notneed to be performed all the time during the laser irradiation. Thefocal point of the laser beam may be adjusted once before thesemiconductor film 206 moves in the X-axis direction. In the X-axisdirection, the focal point is always on the semiconductor film byadjusting the focal point once as above; therefore, the homogeneouslaser irradiation can be performed.

In other words, the focal point of the laser beam may be adjusted to beon the semiconductor film 206 after annealing the semiconductor film 206from one end to the other end in the X-axis direction and before movingthe semiconductor film 206 in the Y-axis direction and again in theX-axis direction. Moreover, when the glass substrate has a wide swell ora complex swell, the semiconductor film 206 may be moved in the Y-axisdirection while controlling the distance between the cylindrical lens103 and the semiconductor film 206 by the autofocusing mechanism asneeded.

The semiconductor film 206 is moved at the speed appropriate for thecrystallization in the X-axis direction where the annealing isperformed. Specifically, the semiconductor film 206 is moved in theX-axis direction at the speed from 100 mm/s to 20 m/s, preferably from10 to 100 cm/s. Within this range of speed, the large crystal grain canbe obtained by the annealing. When the speed is 20 m/s or more, thecrystal does not grow in the scanning direction of the laser beam.Meanwhile, the semiconductor film 206 is moved much slowly in the Y-axisdirection where the annealed position is adjusted than in the X-axisdirection. Specifically, the speed is preferably 100 mm/s or less tocontrol the annealed position accurately.

The same autofocusing mechanism as that shown in the embodiment mode 1can be used. The second laser beam emitted from the laser oscillator 109is incident into the semiconductor film 206 through two cylindricallenses 110 and 111, and the laser beam reflected on the semiconductorfilm 206 is detected by the four-array photodetectors 112. The Z-axisstage 116 is adjusted based on the condition detected by the four-arrayphotodetectors 112 so that the distance between the cylindrical lens 104and the semiconductor film 206 is kept constant.

Although this embodiment mode has described the example of the laserirradiation to the semiconductor film formed over the glass substratehaving the wide swell in one direction, the present invention is notlimited to this. The laser irradiation in consideration of the swell asdescribed above can be performed to any kinds of irradiation objectssuch as a semiconductor, metal, an organic resin film, glass, andplastic which have the swell.

As shown in the embodiment mode 2, when the laser irradiation isperformed in consideration of the swell of the irradiation object, theautofocusing is not necessary all the time. This can increase theprocessing efficiency.

Embodiment Mode 3

This embodiment mode describes a laser irradiation method in which thedistance between a lens and an irradiation object is adjusted by movingan optical system including the lens with reference to FIGS. 4 to 7C.

In FIG. 4, a first laser beam is emitted from a laser oscillator 401 (aCW laser or a pulsed laser with a repetition rate of 10 MHz or more),and reflected on a mirror 402. Then, the laser beam is incidentvertically into an irradiation object 405. The laser beam incidentvertically into the irradiation object 405 is then incident into anoptical system 404 whose height can be controlled by an autofocusingmechanism 403. After that, the laser beam is condensed so as to belinear on the irradiation object 405.

When the CW laser oscillator is used, the first laser beam is madeincident into the irradiation object 405 at a certain angle.

As shown in the embodiment mode 2, when the swell exists in theirradiation object 405, the linear beam is formed so that its short sideis in parallel to the direction where the irradiation object 405 hasfewer swells. The movement of the irradiation object 405 is controlledby an X-axis stage 406 and a Y-axis stage 407. The autofocusingmechanism 403 can move up and down with an autofocusing mechanism 408.

The laser irradiation to the irradiation object 405 may be performedwhile moving the X-axis stage 406 and the Y-axis stage 407 over whichthe irradiation object 405 is mounted. Moreover, the laser irradiationmay be performed while moving the laser beam.

The optical system 404 is described in more detail with reference toFIG. 5. FIG. 5 is a cross-sectional view of the optical system 404, andthe same reference numerals are given to the same parts in the FIGS. 4and 5. The optical system 404 includes two cylindrical lenses 610 and611 acting on different directions respectively. In this embodiment, thecylindrical lens 610 has a focal length of 300 mm and acts on only along-side direction of the linear beam, and the cylindrical lens 611 hasa focal length of 15 mm and acts on only a short-side direction of thelinear beam. By using the cylindrical lenses 610 and 611, the laser beamis shaped into a linear spot on the irradiation object 405. The beamspot has a size of approximately 10 μm in the short-side direction andapproximately 300 μm in the long-side direction.

Next, the autofocusing mechanism 403 is described with reference to FIG.6. In FIG. 6, the optical system 404 can move microscopically by a voicecoil 601, a magnet 602, and an iron core 603 which wrap around theoptical system 404 when a drive current flows from a servo circuit tothe voice coil 601.

Next, the autofocusing mechanism 408 is described with reference toFIGS. 7A to 7C. A second laser beam emitted from a laser oscillator 701is incident into the irradiation object 405 through a convex sphericallens 704 and a cylindrical lens 705, and the reflected laser beam isdetected by four-array photodetectors 706 to measure the distancebetween the irradiation object 405 and the autofocusing mechanism 408.In accordance with the result of the measurement, the autofocusingmechanism 403 moves the optical system 404 up and down to control thedistance between the optical system 404 and the irradiation object 405.

The method for measuring the distance between the autofocusing mechanism408 and the irradiation object 405 is described. In FIGS. 7A to 7C, Apolarizing direction of the laser beam emitted from the laser oscillator701 is rotated by 90° with a λ/2 waveplate 702. After that, the laserbeam passes through a beam splitter 703 and is then condensed by theconvex spherical lens 704.

When the irradiation object 405 is at the focal point of the convexspherical lens 704 (FIG. 7A), the laser beam reflected on theirradiation object 405 travels along the same optical path as that wherethe laser beam is incident into the irradiation object 405, and then thelaser beam is incident into the convex spherical lens 704. Then, a partof the laser beam is deflected by the beam splitter 703 and is incidentinto the cylindrical lens 705.

The cylindrical lens 705 is a condensing lens acting on only onedirection, and a dotted line indicates an optical path of the laser beamin a direction on which the cylindrical lens 705 acts. The solid lineindicates an optical path of the laser beam in a direction on which thecylindrical lens 705 does not act. Here, the beam spot on the four-arrayphotodetectors 706 is circular.

When the irradiation object 405 is before the focal point of the convexspherical lens 704 (FIG. 7B), the laser beam reflected on theirradiation object 405 travels along an optical path inner than theoptical path when the laser beam is incident, and then the laser beam isincident into the convex spherical lens 704. After that, a part of thelaser beam is deflected by the beam splitter 703, and is incident intothe cylindrical lens 705.

The cylindrical lens 705 is a condensing lens acting on only onedirection. The dotted line indicates an optical path of the laser beamin a direction on which the cylindrical lens 705 acts. The solid lineindicates an optical path of the laser beam in a direction on which thecylindrical lens 705 does not act. Here, the beam spot on the four-arrayphotodetectors 706 is elliptical.

When the irradiation object 405 is after the focal point of the convexspherical lens 704 (FIG. 7C), the laser beam reflected on theirradiation object 405 travels along an optical path outer than theoptical path when the laser beam is incident, and then the laser beam isincident into the convex spherical lens 704. After that, a part of thelaser beam is deflected by the beam splitter 703, and incident into thecylindrical lens 705.

The cylindrical lens 705 is a condensing lens acting on only onedirection. The dotted line indicates an optical path of the laser beamin a direction on which the cylindrical lens 705 acts, and the solidline indicates an optical path of the laser beam in a direction on whichcylindrical lens 705 does not act. Here, the beam spot on the four-arrayphotodetectors 706 is elliptical, which is rotated by 90° to the ellipseshown in FIG. 7B.

Therefore, since the beam spot has different shapes on the four-arrayphotodetectors depending on the position of the irradiation object 405,the current value detected by each of the four-array photodetectors isdifferent. Thus, the distance between the irradiation object 405 and theautofocusing mechanism 408 can be measured. When the autofocusingmechanism 408 works with the autofocusing mechanism 403, the distancebetween the optical system 404 and the irradiation object 405 can bemade constant.

The present embodiment mode 3 can be freely combined with the embodimentmode 1 or 2.

Embodiment Mode 4

With reference to FIGS. 9 and 10, this embodiment mode describes anexample of laser irradiation using the autofocusing by one laseroscillator.

In FIG. 9, a laser beam emitted from a laser oscillator 101 is reflectedon a mirror 102 so that the traveling direction of the laser beamchanges to be oblique with respect to a surface of an irradiation object106. After that, the laser beam is incident into the cylindrical lenses103 and 104 which can respectively condense the laser beam in differentdirections, and the laser beam is condensed so that a linear beam spot105 is formed on the irradiation object 106.

The irradiation object 106 can be moved by a Z-axis stage 116, an X-axisstage 117, and a Y-axis stage 118. The Z-axis stage 116 can adjust thetilt of the irradiation object 106 and move the irradiation object 106upward and downward.

Moreover, an autofocusing mechanism for keeping the distance between theirradiation object 106 and the cylindrical lenses 103 and 104 constantis provided. In this embodiment mode, the laser beam emitted from thelaser oscillator 101 is made incident obliquely into the irradiationobject 106, and the reflected laser beam is detected by the four-arrayphotodetectors 112, and thus, the autofocusing is performed. In otherwords, the laser beam emitted from the laser oscillator 101 is also usedas a laser beam for the autofocusing. For example, when the irradiationobject 106 is a semiconductor film, the laser beam emitted from thelaser oscillator 101 can work both as the laser beam for annealing thesemiconductor film and as the laser beam for the autofocusing.

The distance between the irradiation object 106 and the cylindricallenses 103 and 104 can be controlled by detecting the laser beamreflected on the irradiation object 106 using the four-arrayphotodetectors in the same way as the configuration shown in FIG. 2 andFIGS. 3A to 3E.

It is preferable to use the CW laser oscillator in this case. When theCW laser oscillator is used in the laser irradiation, however, theincident laser beam may interfere with the laser beam reflected on therear surface of the irradiation object 106 on the irradiation object106. To avoid the interference of the laser beams, the laser beam may bemade incident into the irradiation object 106 at a certain angle or moreso that the incident beam does not overlap the reflected beam on theirradiation object 106. Since the FIG. 9 shows the configuration inwhich the laser beam is incident obliquely, this configuration issuitable for the case of using the CW laser.

FIG. 10 shows a laser irradiation method in which the laser beam isincident vertically and the autofocusing is performed by one laseroscillator.

A laser oscillator 201 is a mode-locked pulsed laser oscillator with arepetition rate of 10 MHz or more. A polarizing direction of the laserbeam emitted from the laser oscillator 201 is rotated by 90° with apolarizing plate 202. After that, the laser beam passes through a beamsplitter 203, and is condensed on an irradiation object 207 by acondensing lens 204. The condensed laser beam can be used to perform thelaser irradiation such as annealing.

As shown in FIGS. 7A to 7C, the laser beam reflected on the irradiationobject 207 is incident into the condensing lens 204, and detected byfour-array photodetectors 209 through the beam splitter 203 and thecylindrical lens 208. The detected laser beam is converted into anelectric signal by the four-array photodetectors 209. By moving thecondensing lens 204 or the irradiation object 207 so that the electricsignals detected by the respective photodetectors are equal, thedistance between the condensing lens and the irradiation object can bemade constant.

As shown in FIG. 10, when the laser beam is incident vertically into theirradiation object 207, for example, a laser having a short pulse widthof several tens ps or less may be used. Even when the short pulsed laserbeam is incident vertically, the interference between the incident beamand the laser beam reflected on the rear surface of the irradiationobject 207 does not affect the homogeneous laser irradiation.Accordingly, in the case of using the laser having a short pulse widthof several tens ps or less, the homogeneous laser irradiation can beperformed without being affected by the interference of the beam whenthe laser beam is delivered to the irradiation object vertically.

When the irradiation object has the swell, the autofocusing may beperformed in consideration of the swell as shown in the embodiment mode2. This embodiment mode 4 can be freely combined with any one of theembodiment modes 1 to 3.

Embodiment Mode 5

The present invention can be applied to the laser irradiation performedto any object whose thickness is not even. Moreover, the presentinvention can be applied not only to laser irradiating but also toelectron beam imaging or ion beam imaging. This embodiment modedescribes a laser irradiation method when using a laser direct imagingsystem with reference to FIG. 14.

As shown in FIG. 14, a laser direct imaging system 1001 includes acomputer 1002 (hereinafter referred to as a PC) for executing variouscontrols in the laser irradiation; a laser oscillator 1003 for emittingthe laser beam; a power source 1004 of the laser oscillator 1003; anoptical system 1005 for attenuating the laser beam (an ND filter); anacousto-optic modulator (AOM) 1006 for modulating the intensity of thelaser beam; an optical system 1007 including a lens for reducing thecross section of the laser beam, a mirror for changing the optical pathof the laser beam, and the like; a substrate-moving mechanism 1009including an X-axis stage and a Y-axis stage; a D/A converter 1010 fordigital-analog converting the control data outputted from the PC; adriver 1011 for controlling the acousto-optic modulator 1006 inaccordance with the analog voltage outputted from the D/A converter1010; and a driver 1012 for outputting a driver signal to drive thesubstrate-moving mechanism 1009. An autofocusing mechanism 1013 is alsoprovided.

The laser oscillator 1003 may be a laser oscillator capable of emittingan ultraviolet, visible, or infrared beam. Specifically, the laseroscillator 1003 may be, for example, an ArF excimer laser, a KrF excimerlaser, a XeCl excimer laser, or a Xe excimer laser. Moreover, a gaslaser oscillator such as a He laser, a He—Cd laser, an Ar laser, a He—Nelaser, or a HF laser can be used. In addition, a solid-state laseroscillator using a crystal such as YAG, GdVO₄, YVO₄, YLF, or YAlO₃ eachof which is doped with Cr, Nd, Er, Ho, Ce, Co, Ti, or Tm can be used.Furthermore, a semiconductor laser oscillator such as a GaN laser, aGaAs laser, a GaAlAs laser, or an InGaAsP laser can be used. When thesolid-state laser oscillator is used, it is preferable to use thefundamental wave or any one of the second to fifth harmonics.

Next, the laser irradiation method using the laser direct imaging systemis described. When a substrate 1008 is mounted over the substrate-movingmechanism 1009, the PC 1002 detects the position of a marker formed overthe substrate using a camera (not shown). Subsequently, the PC 1002produces motion data for moving the substrate-moving mechanism 1009based on the detected positional data of the marker and the imagepattern data inputted in advance.

Then, after the optical system 1005 attenuates the laser beam emittedfrom the laser oscillator 1003, the acousto-optic modulator 1006controls the amount of the light emission so as to be the predeterminedamount in such a way that the PC 1002 controls the amount of the laserbeam outputted from the acousto-optic modulator 1006 through the driver1011. Meanwhile, the laser beam emitted from the acousto-optic modulator1006 passes through the optical system 1007 so that the optical path andthe beam spot shape of the laser beam are changed. After condensing thelaser beam by the lens, the laser beam is delivered to a light-absorbinglayer formed over the substrate.

Here, the substrate-moving mechanism 1009 is controlled so as to move inthe X-direction and the Y-direction based on the motion data produced bythe PC 1002. As a result, a predetermined region is irradiated with thelaser beam, and the energy density of the laser beam is converted intoheat energy in the light-absorbing layer.

In the case of the laser irradiation using the laser direct imagingsystem, it is necessary to focus the beam spot of the laser beam on thelight-absorbing layer formed over the substrate through the lens.Accordingly, the distance between the optical system 1007 and thesubstrate 1008 is made the same using the autofocusing mechanism 1013 asshown in the embodiment mode 1 or 3. Moreover, when the pattern isformed over the substrate such as a glass substrate which has the swellby the laser direct imaging system, the autofocusing mechanism can beused in consideration of the swell as shown in the embodiment mode 2.The distance between the optical system 1007 and the substrate 1008 maybe controlled by moving the optical system 1007 as shown in FIG. 4 or bymoving the substrate 1008 as shown in FIG. 1.

To form a microscopic pattern by the laser direct imaging system, thebeam spot needs to be small. This leads to the problem of shallow focaldepth. For this reason, it is very effective to use the autofocusingmechanism in the laser irradiation by the laser direct imaging system.

The present embodiment mode 5 can be freely combined with any one of theembodiment modes 1 to 4.

Embodiment Mode 6

With reference to FIG. 15, the embodiment mode 6 describes an example ofthe laser irradiation by moving both of a laser beam and a scanningstage with an irradiation object mounted.

In FIG. 15, an irradiation object 805 is mounted over a rotating stage803, and the rotating stage 803 is mounted over an X-axis scanning stage801 which moves in one direction of an X-axis direction.

Moreover, a Y-axis scanning stage 804 is provided so as to bridge overthe X-axis scanning stage 801. The Y-axis scanning stage 804 has a laseroscillator 807 for emitting the laser beam and an optical system 808 forcondensing the laser beam on the irradiation object. It is preferablethat the beam spot formed on the irradiation object by the opticalsystem 808 is elongate, for example rectangular, elliptical, or linear,because the laser irradiation can be performed effectively. The laseroscillator 807 and the optical system 808 can be moved in the Y-axisdirection.

The laser oscillator 807 is not limited in particular, and it may be aCW laser oscillator or a pulsed laser oscillator. Moreover, the laseroscillator 807 may be a semiconductor laser. Since the semiconductorlaser is compact, it has an advantage that it can be moved easily.

An autofocusing mechanism 810 for keeping the distance between theoptical system 808 and the irradiation object 805 constant is provided.The autofocusing may be performed with any one of the configurationsshown in the embodiment modes 1 to 5. In this embodiment mode, thedistance between the optical system 808 and the irradiation object 805is measured with the configuration shown in FIGS. 7A to 7C. Based on theresult of the measurement, a Z-axis stage 802 is moved to control thedistance between the optical system 808 and the irradiation object 805.Although the irradiation object 805 is moved in this embodiment mode,the optical system 808 may be moved in the Z-axis direction to controlthe distance between the optical system 808 and the irradiation object805.

When the irradiation object 805 has the swell as shown in FIG. 8, thelaser irradiation is performed in consideration of the swell. Forexample, the laser irradiation may be performed as follows when theirradiation object 805 has the swell along the Y-axis direction.

First, a beam spot is formed so that its short side is parallel to theX-axis direction, and the irradiation object 805 is moved in the X-axisdirection. After irradiating the irradiation object 805 once from oneend thereof to the other end, the laser oscillator 807 and the opticalsystem 808 provided to the Y-axis scanning stage 804 are moved in theY-axis direction. After the laser oscillator 807 and the optical system808 are moved in the Y-axis direction, the autofocusing mechanism 810corrects the distance between the optical system 808 and the irradiationobject 805 which has been displaced due to the swell. Then, the laserbeam is delivered to the irradiation object 805 from one end thereof tothe other end by moving the irradiation object in the direction oppositeto the previous X-axis direction, and the laser oscillator 807 is movedin the Y-axis direction again. By repeating the above operation, thelaser irradiation can be performed homogeneously to the whole surface ofthe substrate even when the substrate has the swell.

The movement in the X-axis direction or the Y-axis direction at thelaser irradiation may be set appropriately by a practitioner. Forexample, when a semiconductor film as the irradiation object 805 iscrystallized by the laser irradiation, the semiconductor film is movedin the X-axis direction at the speed appropriate for thecrystallization. The moving speed is preferably in the range of 100 nm/sto 20 m/s, more preferably 10 to 100 cm/s. Moreover, when the laseroscillator 807 and the optical system 808 are moved in the direction(Y-axis direction) parallel to the long-side direction of the beam spot,it is preferable to move them correctly in order to control theirradiation position of the laser beam.

In this case, the laser oscillator 807 is moved slowly in the Y-axisdirection, and the irradiation object 805 is moved in the X-axisdirection. However, they may be opposite. Further, the laser oscillator807 may be moved in both X-axis direction and Y-axis direction withoutmoving the irradiation object 805.

The embodiment mode 6 can be freely combined with any one of theembodiment modes 1 to 5.

Embodiment Mode 7

This embodiment mode describes a laser irradiation method different fromthe above embodiment mode. Specifically, an autofocusing mechanism inthis embodiment mode is different from that in the above embodimentmode.

FIGS. 17A and 17B show an example of the laser irradiation method usinga contact displacement sensor as the autofocusing mechanism. Thisembodiment mode shows the step of annealing a semiconductor film 906 byirradiating the semiconductor film 906 obliquely with the laser beam.

In FIGS. 17A and 17B, a laser beam emitted from a laser oscillator 101is reflected on a mirror 102, and incident obliquely into thesemiconductor film 906 through cylindrical lenses 103 and 104 to form alinear beam spot 105 on the semiconductor film 906. The cylindricallenses 103 and 104 act on different directions respectively. In thisembodiment mode, the laser oscillator 101 is a CW laser oscillator.

The semiconductor film 906 can be moved by the Z-axis stage 116, theX-axis stage 117, and the Y-axis stage 118. The Z-axis stage 116 canadjust the tilt of the semiconductor film 906 and move it upward ordownward. The whole surface of the semiconductor film 906 can beannealed by irradiating the semiconductor film 906 with the laser beamwhile moving the semiconductor film 906 relative to the laser beam.

An autofocusing mechanism is provided to keep the distance between thesemiconductor film 906 and the cylindrical lenses 103 and 104 constant.In this embodiment mode, a contact displacement sensor 901 is used tocontrol the distance between the semiconductor film 906 and thecylindrical lenses 103 and 104 by contacting the semiconductor film 906directly. The contact displacement sensor 901 may be any contactdisplacement sensor when it can control the distance in upward anddownward directions by contacting the semiconductor film 906.

When the semiconductor film 906 is annealed by the laser irradiationusing the CW laser as the laser oscillator 101, two regions aregenerally formed in the irradiated portion. One of them is a largecrystal grain region 903 in which the crystal grain is large and theother is an inferior crystallinity region 904 in which thecrystallization is not performed sufficiently. Since the beam spot 105has power density distribution, the inferior crystallinity region 904 isformed in a part of the semiconductor film 906 corresponding to theopposite ends of the beam spot 105. Generally, since the crystallizationis not performed sufficiently in the inferior crystallinity region 904,the inferior crystallinity region 904 is not suitable for manufacturinga semiconductor element; therefore it is removed in the following step.

When the contact displacement sensor 901 is used as the autofocusingmechanism, a probe of the contact displacement sensor 901 directlycontacts the semiconductor film 906, which may result in that a part ofthe semiconductor film 906 where the probe contacts is contaminated withthe impurity or damaged. However, in the case of using the CW laser asdescribed above, such concerns can be reduced when the probe contactsthe inferior crystallinity region 904, which is formed by the CW laserand will be removed in the following step, to measure the displacementof the semiconductor film 906 in the upward or downward direction. Thus,the autofocusing can be performed without affecting the semiconductorfilm 906.

To measure the distance between the semiconductor film 906 and each ofthe cylindrical lenses 103 and 104 accurately, it is preferable tomeasure by contacting the probe 902 of the contact displacement sensorin the vicinity of the part of the semiconductor film where the laserbeam is delivered. In this embodiment mode, since the laser beam isincident obliquely, the contact displacement sensor 901 can be providedeasily over the beam spot 105 formed on the semiconductor film 906.

Although this embodiment mode has shown the example of using the CWlaser, a pulsed laser with a repetition rate of 10 MHz or more may beused. The autofocusing mechanism may be not only the contactdisplacement sensor but also an electrostatic capacity displacementsensor, an eddy current displacement sensor, or the like.

This embodiment mode 7 can be freely combined with any one of theembodiment modes 1 to 6.

Embodiment Mode 8

This embodiment mode describes an example of a method for manufacturinga semiconductor device using a laser irradiation method of the presentinvention. Although this embodiment mode describes a light-emittingdevice as one of semiconductor devices, the semiconductor device whichcan be manufactured by the present invention is not limited to thelight-emitting device, and it may be a liquid-crystal display device orother semiconductor device.

The light-emitting device is a semiconductor device having alight-emitting element and a unit for supplying current to thelight-emitting element in each of a plurality of pixels. Thelight-emitting element typified by an OLED (Organic Light-EmittingDiode) has an anode, a cathode, and a layer (electroluminescent layer)including an electroluminescent material that gives luminescence byapplying an electric field thereto. The electroluminescent layer is asingle layer or multilayers formed between the anode and the cathode.These layers may include an inorganic compound.

First, a substrate 500 over which a TFT (thin film transistor) will beformed is prepared as shown in FIG. 11A. The substrate 500 may be, forexample, a glass substrate made from barium borosilicate glass oraluminoborosilicate glass. Moreover, a quartz substrate or a ceramicsubstrate may be used. Furthermore, a metal or semiconductor substratewith an insulating film formed thereover may be used. Although aflexible substrate made from synthetic resin such as plastic isgenerally inferior to the above substrates in the heat resistance, theflexible substrate can be used when it can resist the processingtemperature in the manufacturing steps. A surface of the substrate 500may be polished by a CMP method or the like so as to be planarized.

Next, a base film 501 including an insulating material such as siliconoxide, silicon nitride, or silicon oxynitride may be formed over thesubstrate 500 by a known method (a sputtering method, an LPCVD method, aplasma CVD method, or the like). Although the base film 501 is a singleinsulating film in this embodiment mode, the base film 501 may includetwo or more insulating layers.

Next, an amorphous semiconductor film 502 is formed in 50 nm thick overthe base film 501 by the plasma CVD method. Then, a dehydrogenationprocess is performed. Depending on the hydrogen content in the amorphoussemiconductor film, it is preferable that the amorphous semiconductorfilm is dehydrogenated at temperatures from 400 to 550° C. for severalhours. The following crystallization process is desirably performedafter the hydrogen content in the amorphous semiconductor film decreasesto 5 atoms % or less by the dehydrogenation process. The amorphoussemiconductor film may be formed by another method such as thesputtering method or the evaporation method. In any method, it ispreferable to decrease the impurity element in the amorphoussemiconductor film such as oxygen or nitrogen sufficiently.

Not only silicon but also silicon germanium can be used as thesemiconductor. When the silicon germanium is used, the density of thegermanium may range from approximately 0.01 to 4.5 atomic %.

In this embodiment mode, both of the base film 501 and the amorphoussemiconductor film 502 are formed by the plasma CVD method. In thiscase, the base film 501 and the amorphous semiconductor film 502 may beformed continuously in vacuum. By forming the base film 501 and theamorphous semiconductor film 502 continuously without exposing them tothe air, it is possible to prevent the interface therebetween from beingcontaminated and to reduce the variation of the characteristic of theTFTs to be manufactured.

Next, the amorphous semiconductor film 502 is crystallized by a lasercrystallization method as shown in FIG. 11B using the autofocusingmechanism of the present invention. The amorphous semiconductor film 502may be crystallized by not only the laser crystallization method butalso other known crystallization method such as a thermalcrystallization method using RTA or an annealing furnace or a thermalcrystallization method using a metal element for promoting thecrystallization.

When the amorphous semiconductor film is crystallized by the second,third, or fourth harmonic of the fundamental wave of a continuous wavesolid-state laser, a large crystal grain can be obtained. Typically, itis desirable to use the second (532 nm) or third harmonic (355 nm) of aNd:YVO₄ laser (fundamental wavelength 1064 nm). Specifically, the laserbeam emitted from the continuous wave YVO₄ laser is converted into theharmonic with a power of 10 W by a non-linear optical element. Thenon-linear optical element may be set in the resonator with the YVO₄crystal to emit the harmonic. Then, the amorphous semiconductor film,which is the processing object, is irradiated with the laser beam thatis preferably shaped into a rectangular or elliptical spot on theirradiation surface by the optical system. The energy density needs tobe in the range of approximately 0.01 to 100 MW/cm² (preferably 0.1 to10 MW/cm²). The laser irradiation is performed while moving theamorphous semiconductor film 502 relative to the laser beam at the speedfrom approximately 10 to 2000 cm/s. When the substrate has the swell,the laser irradiation is preferably performed in consideration of theswell as shown in FIG. 8.

The laser irradiation can be performed using a continuous wave gas orsolid-state laser. The continuous wave gas laser is, for example, an Arlaser or a Kr laser. The continuous wave solid-state laser is, forexample, a YAG laser, a YVO₄ laser, a GdVO₄ laser, a YLF laser, a YAlO₃laser, an alexandrite laser, a Ti: Sapphire laser, or a Y₂O₃ laser. Asthe continuous wave solid-state laser, a laser using a crystal such asYAG, YVO₄, YLF, YAlO₃, GdVO₄, or the like each of which is doped withCr, Nd, Er, Ho, Ce, Co, Ti, Yb, or Tm can be also used. Although thefundamental wavelengths of these lasers depend on the doped element,they are approximately 1 μm. The harmonic of the fundamental wave can beobtained by using the non-linear optical element.

A crystalline semiconductor film 503 having its crystallinity enhancedis formed by performing the laser crystallization as above.

Next, the crystalline semiconductor film 503 is patterned into a desiredshape to form island-shaped semiconductor films 504 to 506 which becomeactive layers of TFTs (FIG. 11C). To control the threshold value of theTFT, a small amount of impurity elements (boron or phosphorous) may bedoped after forming the island-shaped semiconductor films 504 to 506.

Next, a gate insulating film 507 mainly including silicon oxide orsilicon nitride is formed so as to cover the island-shaped semiconductorfilms 504 to 506 to be active layers as shown in FIG. 11D. In thisembodiment mode, a silicon oxide film is formed by the plasma CVD methodunder the condition where TEOS (tetraethyl orthosilicate) is mixed withO₂, the reaction pressure is 40 Pa, the substrate temperature rangesfrom 300 to 400° C., and the electricity is discharged with highfrequency (13.56 MHz) at electric density from 0.5 to 0.8 W/cm². Thesilicon oxide film manufactured thus obtains good characteristic as thegate insulating film by performing the thermal annealing at 400 to 500°C. thereafter. The gate insulating film may be formed of aluminumnitride. The aluminum nitride is relatively high in heat conductivity,thereby being able to diffuse the heat generated in the TFT effectively.The gate insulating film may be multilayers in which aluminum nitride isformed over silicon oxide or silicon oxynitride not including aluminum.

Then, as shown in FIG. 11E, a conductive film is formed in 100 to 500 nmthick over the gate insulating film 507 and patterned to form gateelectrodes 508 to 510.

In this embodiment mode, the gate electrode may be formed of an elementselected from the group consisting of Ta, W, Ti, Mo, Al, and Cu.Moreover, the gate electrode may be formed of an alloy material or acompound material mainly including any one of the above elements.Furthermore, the gate electrode may be formed of the semiconductor filmtypified by a poly-crystalline silicon film with the impurity elementsuch as phosphorous doped. The gate electrode may include a singleconductive film or plural conductive films.

When the gate electrode is formed of two conductive films, preferablecombinations are tantalum nitride (TaN) as the first conductive film andW as the second conductive film, tantalum nitride (TaN) as the firstconductive film and Al as the second conductive film, and tantalumnitride (TaN) as the first conductive film and Cu as the secondconductive film. Moreover, the first and second conductive films may bea semiconductor film typified by a poly-crystalline silicon film dopedwith the impurity element such as phosphorous or may be formed of AgPdCualloy.

The structure of the gate electrode is not limited to the two-layerstructure, and it may be a three-layer structure in which, for example,a tungsten film, an aluminum-silicon alloy (Al—Si) film, and a titaniumnitride film are laminated sequentially. A tungsten nitride film may beused instead of the tungsten film, an aluminum-titanium alloy (Al—Ti)film may be used instead of the aluminum-silicon alloy (Al—Si) film, anda titanium film may be used instead of the titanium nitride film. It isimportant to select the optimum etching method and the optimum kind ofetchant in accordance with the material of the conductive film.

Next, n-type impurity regions 512 to 517 are formed by adding an n-typeimpurity element. In this embodiment, an ion doping method usingphosphin (PH₃) is employed.

Next, as shown in FIG. 12A, p-type impurity regions 518 and 519 areformed by adding a p-type impurity element to a region where a p-channelTFT is formed while covering the region where an n-channel TFT is formedwith a resist mask 520. In this embodiment mode, an ion doping methodusing diborane (B₂H₆) is employed.

Then, the doped impurity elements in the respective island-shapedsemiconductor films are activated for the purpose of controlling theelectrical conductivity type. This activation process is performed by athermal annealing method using the annealing furnace. Besides, the laserannealing method and the rapid thermal annealing (RTA) method can beapplied. The thermal annealing is performed with the oxygen density of 1ppm or less, preferably 0.1 ppm or less, in the nitrogenous atmosphereof 400 to 700° C., typically 500 to 600° C. In this embodiment mode, theheat treatment is performed at 500° C. for four hours. However, when thegate electrodes 508 to 510 are sensitive to heat, it is preferable toperform the activation process after forming the interlayer insulatingfilm (mainly including silicon) in order to protect a wiring or thelike.

In the case of employing the laser annealing method, the laser used inthe crystallization can be used. In the activation process, the scanningspeed of the laser beam is the same as that in the crystallization, andthe energy density needs to be in the range of approximately 0.01 to 100MW/cm² (preferably 0.01 to 10 MW/cm²). The continuous wave laser may beused in the crystallization, and the pulsed laser may be used in theactivation.

Next, heat treatment is performed at 300 to 450° C. for 1 to 12 hours inthe atmosphere including hydrogen by 3 to 100% to hydrogenate theisland-shaped semiconductor film. This is to terminate the dangling bondin the semiconductor film by the hydrogen excited thermally. As othermeans of hydrogenation, plasma hydrogenation may be performed (usinghydrogen excited in plasma).

Next, as shown in FIG. 12B, a first inorganic insulating film 521 isformed of silicon oxynitride in 10 to 200 nm thick by a CVD method. Thefirst inorganic insulating film is not limited to the silicon oxynitridefilm, and it may be an inorganic insulating film including nitrogen thatcan suppress the access of the moisture to an organic resin film to beformed afterward. For example, silicon nitride, aluminum nitride, oraluminum oxynitride can be used. It is noted that aluminum nitride isrelatively high in heat conductivity, thereby being able to diffuse theheat generated in the TFT or the light-emitting element effectively.

An organic resin film 522 is formed of a positive photosensitive organicresin over the first inorganic insulating film 521. Although the organicresin film 522 is formed of the positive photosensitive acrylic in thisembodiment mode, the present invention is not limited to this.

In this embodiment mode, the organic resin film 522 is formed byapplying positive photosensitive acrylic by a spin coating method andbaking it thereafter. The thickness of the organic resin film 522 afterthe baking is set in the range of approximately 0.7 to 5 μm (preferably2 to 4 μm).

Next, a part of the organic resin film 522 where an opening portion isto be formed is exposed with the light using a photomask. Then, theorganic resin film is developed using a TMAH (tetramethyl ammoniumhydroxide)-based developing solution, the substrate is dried, and thenthe baking is performed at 220° C. for approximately one hour. As shownin FIG. 12B, the opening portion is formed in the organic resin film522, and the first inorganic insulating film 521 is partially exposed inthe opening portion.

Since the positive photosensitive acrylic is colored to be light brown,it is decolorized in the case where the light is emitted from thelight-emitting element to the substrate side. In this case, thedeveloped photosensitive acrylic is entirely exposed with light againbefore the baking. This exposure is performed so that the photosensitiveacrylic is exposed completely by extending the exposure time or byirradiating with the light having higher intensity than in the formerexposure for forming the opening portion. For example, in the case ofdecolorizing the positive acrylic resin having a thickness of 2 μm withthe use of an equivalent-magnification projecting exposure system(specifically MPA manufactured by Canon Inc.), which utilizesmultiwavelengths including a g-line (436 nm), an h-line (405 nm), and ani-line (365 nm) all of which are in the spectrum of light emitted from asuper-high pressure mercury lamp, the exposure is performed forapproximately 60 seconds. This exposure decolorizes the positive acrylicresin completely.

Although the baking is performed at 220° C. after the development inthis embodiment mode, low-temperature prebaking at approximately 100° C.may be performed between the high-temperature baking at 220° C. and thedevelopment.

Then, a second inorganic insulating film 523 is formed of siliconnitride by an RF sputtering method so as to cover the organic resin film522 and the opening portion where the first inorganic insulating film521 is exposed partially as shown in FIG. 12C. The thickness of thesecond inorganic insulating film 523 preferably ranges fromapproximately 10 to 200 nm. The material of the second inorganicinsulating film is not limited to silicon nitride, and any inorganicinsulating film including nitride that can suppress the access of themoisture to the organic resin film 522 may be used. For example, siliconoxynitride, aluminum nitride, or aluminum oxynitride can be used.

In the case of using the silicon oxynitride film or the aluminumoxynitride film, the proportion between oxygen and nitrogensignificantly affects its barrier property. The higher the proportion ofnitrogen to oxygen is, the higher the barrier property is. Therefore, itis preferable that the oxynitride film includes more nitrogen thanoxygen.

The film formed by the RF sputtering method is highly dense and superiorin barrier property. In the case of forming the silicon oxynitride film,the condition in the RF sputtering method is that the gas flow rate ofN₂, Ar, and N₂O is 31:5:4, the target is Si, the pressure is 0.4 Pa, andthe electric power is 3000 W. As another example, in the case of formingthe silicon nitride film, the condition is that the gas flow rate of N₂and Ar in the chamber is 20:20, the pressure is 0.8 Pa, the electricpower is 3000 W, and the film-forming temperature is 215° C.

The first interlayer insulating film is formed with the organic resinfilm 522, the first inorganic insulating film 521, and the secondinorganic insulating film 523.

Next, as shown in FIG. 12C, a resist mask 524 is formed in the openingportion of the organic resin film 522, and a contact hole is formed tothe gate insulating film 507, the first inorganic insulating film 521,and the second inorganic insulating film 523 by a dry etching method.

Due to the opening of this contact hole, the impurity regions 512 to515, 518, and 519 are partially exposed. The condition of the dryetching is determined appropriately depending on the materials of thegate insulating film 507, the first inorganic insulating film 521, andthe second inorganic insulating film 523. Since the gate insulating film507 is formed with silicon oxide, the first inorganic insulating film521 is formed with silicon oxynitride, and the second inorganicinsulating film 523 is formed with silicon nitride in this embodimentmode, the first inorganic insulating film 521 and the second inorganicinsulating film 523 are etched by using CF₄, O₂, and He as the etchinggas, and then the gate insulating film 507 is etched by using CHF₃.

It is important that the organic resin film 522 is not exposed in theopening portion when being etched.

Next, wirings 526 to 531 connected to the impurity regions 512 to 515,518, and 519 are formed by forming and patterning a conductive film overthe second inorganic insulating film 523 so as to cover the contact hole(FIG. 12D).

Although three conductive films are formed with a 100-nm-thick Ti film,a 300-nm-thick Al film, and a 150-nm-thick Ti film continuously over thesecond inorganic insulating film 523 continuously by the sputteringmethod in this embodiment mode, the present invention is not limited tothis. The conductive film may be a single layer, two layers, or four ormore layers. The material of the conductive film is not limited to theabove description.

As another example of the conductive film, after forming a Ti film, anAl film including Ti may be laminated thereover. Alternatively, afterforming the Ti film, an Al film including W may be laminated thereover.

Next, an organic resin film to be a bank is formed over the secondinorganic insulating film 523. Although a positive photosensitiveacrylic is used in this embodiment mode, the present invention is notlimited to this. In this embodiment mode, the organic resin film isformed by applying the positive photosensitive acrylic by the spincoating method and baking it. The thickness of the organic resin film isset in the range of approximately 0.7 to 5 μm (preferably 2 to 4 μm).

Next, a part of the organic resin film where the opening portion isformed is exposed with light using the photomask. The organic resin filmis developed using a TMAH (tetramethyl ammonium hydroxide)-baseddeveloping solution, the substrate is dried, and then the baking isperformed at 220° C. for approximately one hour. Accordingly, as shownin FIG. 12E, a bank 533 having the opening portion is formed, and thewirings 529 and 531 are partially exposed in the opening portion.

Since the positive photosensitive acrylic is colored to be light brown,it is decolorized in the case where the light is emitted from thelight-emitting element to the substrate side. The decolorization processis performed by the same procedure as that performed to the organicresin film 522.

When the bank 533 is formed of the photosensitive organic resin, thecross sectional shape of the opening portion can be made into round.Therefore, the coverage of the electroluminescent layer and the cathodeto be formed afterward can be improved, and the defect in which thelight-emitting region decreases, which is called shrink, can bedecreased.

Subsequently, as shown in FIG. 13A, a third inorganic insulating film534 is formed of silicon nitride by the RF sputtering method so as tocover the bank 533 and the opening portion where the wirings 529 and 531are partially exposed. The thickness of the third inorganic insulatingfilm 534 is preferably from 10 to 200 nm. The material of the thirdinorganic insulating film 534 is not limited to silicon nitride, and aninorganic insulating material including nitride that can suppress theaccess of the moisture to the bank 533 may be used. For example, siliconoxynitride, aluminum nitride, or aluminum oxynitride can be used.

In the case of using the silicon oxynitride or the aluminum oxynitride,the proportion between oxygen and nitrogen in atomic % significantlyaffects its barrier property. The higher the proportion of nitrogen tooxygen is, the higher the barrier property is. Therefore, it ispreferable that the oxynitride film includes more nitrogen than oxygen.

Next, a resist mask 535 is formed in the opening portion of the bank533, and then a contact hole is formed to the third inorganic insulatingfilm 534 by the dry etching method.

Due to the opening of the contact hole, the wirings 529 and 531 arepartially exposed. The condition of the dry etching is determinedappropriately in accordance with the material of the third inorganicinsulating film 534. In this embodiment mode, since the third inorganicinsulating film 534 is formed of silicon nitride, the third inorganicinsulating film 534 is etched by using CF₄, O₂, and He as the etchinggas.

It is important that the bank 533 is not exposed in the opening portionwhen being etched.

Next, a pixel electrode 540 in contact with the wiring 531 and a leadwiring 541 to obtain the current generated in the diode are formed byforming and patterning a 110-nm-thick transparent conductive film, forexample, IFO film. A transparent conductive film in which zinc oxide(ZnO) is mixed into indium oxide by 2 to 20% may be used. The pixelelectrode 540 will serve as the anode of the light-emitting element(FIG. 13B).

Next, an electroluminescent layer 542 is formed over the pixel electrode540 by the evaporation method, and a cathode (MgAg electrode) 543 isformed further by the evaporation method. Here, it is desirable toremove the moisture completely by heat treatment to the pixel electrode540 before forming the electroluminescent layer 542 and the cathode 543.Although the MgAg electrode is used as the cathode of the light-emittingelement, other known conductive material having low work function, forexample Ca, Al, CaF, MgAg, or AlLi, may be used.

When the cathode is formed of AlLi, the third inorganic insulating film534 including nitrogen can prevent Li in AlLi from entering beyond thethird inorganic insulating film 534 toward the substrate side.

A known material can be used as the electroluminescent layer 542.Although the electroluminescent layer includes two layers of ahole-transporting layer and a light-emitting layer in this embodimentmode, any one or a plurality of a hole-injecting layer, anelectron-injecting layer, and an electron-transporting layer may be alsoprovided. Various examples have been already reported concerning thesecombinations, and any configuration may be employed. For example, SAlq,CAlq, or the like may be used as the electron-transporting layer or thehole-blocking layer.

The thickness of the electroluminescent layer 542 may be set in therange of 10 to 400 nm (typically 60 to 150 nm), and the thickness of thecathode 543 may be set in the range of 80 to 200 nm (typically 100 to150 nm).

Thus, a light-emitting device having a structure shown in FIG. 13B iscompleted. In FIG. 13B, a reference numeral 550 denotes a pixel portionand a reference numeral 551 denotes a driver circuit portion. The partof the pixel portion 550 where the pixel electrode 540, theelectroluminescent layer 542, and the cathode 543 overlap corresponds tothe light-emitting element.

It is noted that the structure of the light-emitting device and thespecific manufacturing method described in this embodiment mode are justan example. The present invention is not limited to the description ofthis embodiment mode.

After the processes up to FIG. 13B are completed, it is preferable topackage (enclose) with a protective film (a laminated film, anultraviolet curable resin film, or the like) that is highly dense andthat hardly degasses or with a light-transmitting cover member so thatthe light-emitting element is not exposed to the air. In this step, thereliability of light-emitting element can be enhanced when the inside ofthe cover member is filled with inert atmosphere or when a materialhaving moisture-absorption property (such as barium oxide) is providedinside.

This embodiment mode 8 can be combined with any one of the embodimentmodes 1 to 7.

Embodiment Mode 9

As electronic instruments using a semiconductor device manufactured byapplying the laser irradiation method of the present invention, thereare a video camera, a digital camera, a goggle type display (head mountdisplay), a navigation system, a sound reproduction device (a car audio,an audio compo, and the like), a computer, a game machine, a mobileinformation terminal (a mobile computer, a mobile phone, a mobile gamemachine, an electronic book, and the like), an image reproduction devicewith a recording medium (specifically, a device for playing therecording medium such as a DVD (digital versatile disc) that is equippedwith a display for displaying the image), and so on. FIGS. 16A to 16Hshow the specific examples of these electronic instruments.

FIG. 16A shows a television receiver machine including a chassis 2001, asupporting stand 2002, a display portion 2003, a speaker portion 2004, avideo input terminal 2005, and the like. The television receiver machinecan be manufactured by applying the laser irradiation method describedin any one of the above embodiment modes 1 to 7 to the process of thedisplay portion 2003 and the like.

FIG. 16B shows a digital camera including a main body 2101, a displayportion 2102, an image receiver portion 2103, an operation key 2104, anexternal connection port 2105, a shutter 2106, and the like. The digitalcamera can be manufactured by applying the laser irradiation methoddescribed in any one of the above embodiment modes 1 to 7 to theprocesses of the display portion 2102, the circuits, and the like.

FIG. 16C shows a computer including a main body 2201, a chassis 2202, adisplay portion 2203, a keyboard 2204, an external connection port 2205,a pointing mouse 2206, and the like. The computer can be manufactured byapplying the laser irradiation method described in any one of the aboveembodiment modes 1 to 7 to the processes of the display portion 2203,the circuits, and the like.

FIG. 16D shows a mobile computer including a main body 2301, a displayportion 2302, a switch 2303, an operation key 2304, an infrared port2305, and the like. The mobile computer can be manufactured by applyingthe laser irradiation method described in any one of the aboveembodiment modes 1 to 7 to the processes of the display portion 2302,the circuits, and the like.

FIG. 16E shows a mobile image reproduction device with a recordingmedium equipped (such as a DVD reproduction device) including a mainbody 2401, a chassis 2402, a display portion A 2403, a display portion B2404, a recording-medium reader portion 2405, an operation key 2406, aspeaker portion 2407, and the like. The display portion A 2403 mainlydisplays image information, while the display portion B 2404 mainlydisplays text information. The image reproduction device can bemanufactured by applying the laser irradiation method described in anyone of the above embodiment modes 1 to 7 to the processes of the displayportions A 2403 and B 2404, the circuits, and the like. The imagereproduction device includes the game machine and the like.

FIG. 16F shows a goggle type display (head mount display) including amain body 2501, a display portion 2502, and an arm portion 2503. Thegoggle type display can be manufactured by applying the laserirradiation method described in any one of the above embodiment modes 1to 7 to the processes of the display portion 2502, the circuits, and thelike.

FIG. 16G shows a video camera including a main body 2601, a displayportion 2602, a chassis 2603, an external connection port 2604, a remotecontroller receiving portion 2605, an image receiver portion 2606, abattery 2607, an audio input portion 2608, an operation key 2609, aneyepiece portion 2610, and the like. The video camera can bemanufactured by applying the laser irradiation method described in anyone of the above embodiment modes 1 to 7 to the processes of the displayportion 2602, the circuits, and the like.

FIG. 16H shows a mobile phone including a main body 2701, a chassis2702, a display portion 2703, an audio input portion 2704, an audiooutput portion 2705, an operation key 2706, an external connection port2707, an antenna 2708, and the like. The mobile phone can bemanufactured by applying the laser irradiation method described in anyone of the above embodiment modes 1 to 7 to the processes of the displayportion 2703, the circuits, and the like.

In addition to the above electronic instruments, a front type or reartype projector may be manufactured by applying the present invention.

As thus described, the present invention can be applied in a wide range,thereby being applicable to the electronic instruments of every field.

The present embodiment mode 9 can be freely combined with any one of theembodiment modes 1 to 8.

1. A laser irradiation method comprising: providing an irradiationobject over a stage; irradiating the irradiation object with a linearbeam spot through an optical system while moving the stage along a firstdirection; and moving the optical system along a second directionperpendicular to the first direction after moving the stage along thefirst direction, wherein a distance between the irradiation object andthe optical system is controlled by an autofocusing mechanism before thestage is moved along the first direction.
 2. The laser irradiationmethod according to claim 1, wherein the linear beam spot is emittedfrom a continuous wave laser oscillator.
 3. The laser irradiation methodaccording to claim 1, wherein the linear beam spot is emitted from asemiconductor laser oscillator.
 4. The laser irradiation methodaccording to claim 1, wherein the autofocusing mechanism comprisesfour-array photodetectors.
 5. A laser irradiation method comprising:providing an irradiation object over a first stage; shaping a laser beamemitted from a laser oscillator into a linear beam spot by using anoptical system provided with a second stage which is provided so as tobridge over the first stage; and irradiating the irradiation object withthe linear beam spot while moving the first stage along a firstdirection, wherein a distance between the irradiation object and theoptical system is controlled by an autofocusing mechanism before thefirst stage is moved along the first direction.
 6. The laser irradiationmethod according to claim 5, wherein the laser oscillator is acontinuous wave laser oscillator.
 7. The laser irradiation methodaccording to claim 5, wherein the laser oscillator is a semiconductorlaser oscillator.
 8. The laser irradiation method according to claim 5,wherein the autofocusing mechanism comprises four-array photodetectors.9. A method for manufacturing a semiconductor device comprising:providing a substrate having a semiconductor film over a stage;irradiating the semiconductor film with a linear beam spot through anoptical system while moving the stage along a first direction; andmoving the optical system along a second direction perpendicular to thefirst direction after moving the stage along the first direction,wherein a distance between the semiconductor film and the optical systemis controlled by an autofocusing mechanism before the stage is movedalong the first direction.
 10. The method for manufacturing thesemiconductor device according to claim 9, wherein the linear beam spotis emitted from a continuous wave laser oscillator.
 11. The method formanufacturing the semiconductor device according to claim 9, wherein thelinear beam spot is emitted from a semiconductor laser oscillator. 12.The method for manufacturing the semiconductor device according to claim9, wherein the autofocusing mechanism comprises four-arrayphotodetectors.
 13. The method for manufacturing the semiconductordevice according to claim 9, wherein the semiconductor film comprisessilicon.
 14. A method for manufacturing a semiconductor devicecomprising: providing a substrate having a semiconductor film over afirst stage; shaping a laser beam emitted from a laser oscillator into alinear beam spot by using an optical system provided with a second stagewhich is provided so as to bridge over the first stage; and irradiatingthe semiconductor film with the linear beam spot while moving the firststage along a first direction, wherein a distance between thesemiconductor film and the optical system is controlled by anautofocusing mechanism before the first stage is moved along the firstdirection.
 15. The method for manufacturing the semiconductor deviceaccording to claim 14, wherein the laser oscillator is a continuous wavelaser oscillator.
 16. The method for manufacturing the semiconductordevice according to claim 14, wherein the laser oscillator is asemiconductor laser oscillator.
 17. The method for manufacturing thesemiconductor device according to claim 14, wherein the autofocusingmechanism comprises four-array photodetectors.
 18. The method formanufacturing the semiconductor device according to claim 14, whereinthe semiconductor film comprises silicon.
 19. A method for manufacturinga semiconductor device comprising: providing a semiconductor over astage; irradiating the semiconductor with a linear beam spot through anoptical system while moving the stage along a first direction; andmoving the optical system along a second direction perpendicular to thefirst direction after moving the stage along the first direction,wherein a distance between the semiconductor and the optical system iscontrolled by an autofocusing mechanism before the stage is moved alongthe first direction.
 20. The method for manufacturing the semiconductordevice according to claim 19, wherein the linear beam spot is emittedfrom a continuous wave laser oscillator.
 21. The method formanufacturing the semiconductor device according to claim 19, whereinthe linear beam spot is emitted from a semiconductor laser oscillator.22. The method for manufacturing the semiconductor device according toclaim 19, wherein the autofocusing mechanism comprises four-arrayphotodetectors.
 23. The method for manufacturing the semiconductordevice according to claim 19, wherein the semiconductor comprisessilicon.
 24. A method for manufacturing a semiconductor devicecomprising: providing a semiconductor over a first stage; shaping alaser beam emitted from a laser oscillator into a linear beam spot byusing an optical system provided with a second stage which is providedso as to bridge over the first stage; and irradiating the semiconductorwith the linear beam spot while moving the first stage along a firstdirection, wherein a distance between the semiconductor and the opticalsystem is controlled by an autofocusing mechanism before the first stageis moved along the first direction.
 25. The method for manufacturing thesemiconductor device according to claim 24, wherein the laser oscillatoris a continuous wave laser oscillator.
 26. The method for manufacturingthe semiconductor device according to claim 24, wherein the laseroscillator is a semiconductor laser oscillator.
 27. The method formanufacturing the semiconductor device according to claim 24, whereinthe autofocusing mechanism comprises four-array photodetectors.
 28. Themethod for manufacturing the semiconductor device according to claim 24,wherein the semiconductor comprises silicon.
 29. A laser irradiationapparatus comprising: a laser oscillator for emitting a laser beam; anoptical system including a lens for condensing the laser beam to form alinear beam spot on a surface of an irradiation object; an X-axis stagefor moving the irradiation object along a first direction; an Y-axisstage for moving the optical system along a second directionperpendicular to the first direction; and an autofocusing mechanism forcontrolling a distance between the irradiation object and the lens,wherein the Y-axis stage is provided so as to bridge over the X-axisstage.
 30. The laser irradiation apparatus according to claim 29,wherein the laser oscillator is a continuous wave laser oscillator. 31.The laser irradiation apparatus according to claim 29, wherein the laseroscillator is a semiconductor laser oscillator.
 32. The laserirradiation apparatus according to claim 29, wherein the autofocusingmechanism comprises four-array photodetectors.